Microtubules are known to play an important role in a variety of intracellular motile processes, including flagellar and ciliary beating axoplasmic transport, secretion, and mitosis. The best documented microtubule-related motile system is the flagellum (cilium) in which the dynein (ATPase) arms both bridge adjacent microtubules and serve as motors for microtubule sliding. The role of microtubules in axoplasmic transport and secretion is less well understood: electron microscopic studies show close associations between organelles and microtubules; drugs which disassemble microtubules either abolish or alter organelle movements. Recent studies have shown that actomyosin might be involved in microtubule-related movements of granules during secretion. The ultrastructural arrangements of the actomyosin and microtubules and the mechanisms by which granule movements occur is, however, unknown. The proposed research will: (a) Investigate the identity and localization of the components necessary for the secretion of insulin in pancreatic cells, (b) Fractionate the cells and isolate the motile components, and (c) Investigate the biochemical mechanisms by which the microtubules participate in the organelle movements. Both high resolution light and electron microscopy will be used to assay the secretory granule movements and the structures involved in the movements.